1. Field of the Invention
This invention relates to automatic package forming, filling and sealing machines involving fasteners, for example with complementary male and female profiles. This type of machine is often referred to as an FFS (xe2x80x9cForm, Fill and Sealxe2x80x9d) machine.
2. Description of the Prior Art
U.S. Pat. No. 4,909,017 to McMahon et al. describes a process in which bags are provided with a fastener when they are formed on an FFS machine. The bags are formed from a film of thermoplastic material. The film is in the form of a strip of material extending between two free edges that are longitudinal with reference to the movement of the film. This film is unrolled upstream of a filling tube. The fastener is positioned on the film, also upstream of the spout and transversely with respect to the direction of movement of the film. The fastener consists of two strips provided with complementary profiles. A first strip of the fastener is welded to the film upstream of the tube, on a portion of the film which is intended to form a first bag wall. The bag is then formed by enveloping the tube and welding the two longitudinal edges of the film. The second fastener is then welded below the tube to a second bag wall.
U.S. Pat. No. 4,655,862 to Christoff et al. also describes a process for forming reclosable bags on FFS machines, in which bags are provided with a fastener that is positioned at right angles to the direction of formation of these bags. This fastener is placed below the filling tube on a film in the form of a single strip. This strip includes at least one fold zone crosswise to the strip so that the strip can be folded back on itself, and areas of the strip that can work together to seal the bag can be brought opposite one another.
It is therefore an object of the present invention is to make the steps involving the support, welding and installation of the fastener on the film easier to perform than in the processes described in the above-cited references.
The above and other beneficial objects are attained by providing a process for the fabrication of a film intended to form the bags, including steps of moving the film and fixing fasteners sequentially on the film and transversely with reference to the direction of movement of the film. The fastener consists of a first strip supporting at least one reclosable profile in engagement with another reclosable profile, which is complementary thereto and supported by a second strip or part of the first strip. The second strip or part of the first strip that supports the other profile will be subsequently fixed to the film. Each strip has at least one web extending substantially laterally on one side of the profile or profiles supported thereby.
These webs give the invention a number of advantages. Due its larger cross-section, a fastener for implementing the process according to the invention is easily moved and positioned. In addition, the webs can be attached at sufficiently low temperatures as to prevent damaging the profiles.
It is also possible for the step of attaching the fastener to the film to be performed by sealing the film with at least one area of these webs different from the area located under the profiles to prevent damage to the profiles during the attaching step.